rpi-firmware: update to latest rpi3-psci-monitor

The last update to rpi3-psci-monitor regressed the Raspberry Pi 3B{,+};
U-Boot would run unbearably slow, taking 30+ seconds easily to transition
into efi loader.

Tom Yan <tom.ty89 gmail com> tracked it down and submitted a fix; update to
that revision.

Approved by: u-boot (manu), manu (ports)